Emergency call redial on different PS domains

ABSTRACT

Systems, methods, and devices of the various aspects may enable a mobile communication device to make a second emergency call attempt in a packet switched (PS) domain in response to determining that a first emergency call attempt in a PS domain failed. The various aspects may enable a second emergency call attempt in a PS domain without requiring the mobile communication device to attempt an emergency call in a circuit switched (CS) domain in response to determining that a first emergency call attempt in a PS domain failed.

RELATED APPLICATIONS

This application claims the benefit of priority to U.S. ProvisionalApplication No. 62/769,526, entitled “Emergency Call Redial On DifferentPS Domains” filed Nov. 19, 2018, the entire contents of which are herebyincorporated by reference for all purposes.

BACKGROUND

Cellular and wireless communication technologies have seen explosivegrowth over the past several years and are being used to supportcommunications between a host of different types of communicationdevices, such as mobile communication devices, vehicle-basedcommunication devices, infrastructure communication devices, networkcommunication devices, etc. This growth has been fueled by bettercommunications hardware, larger networks, and more reliable protocols.

Some designs of mobile communication devices—such as smart phones,tablet computers, and laptop computers—support multiple subscriptions(e.g., multi-subscriber identity module (multi-SIM) mobile communicationdevices) that provide users with access to multiple separate mobileprovider networks. Examples of radio access technologies (RATs) used bymobile provider networks include third generation wireless mobilecommunication technologies (3G) (e.g., global system for mobilecommunications (GSM) evolution (EDGE) systems, code division multipleaccess (CDMA) 2000 systems, Wideband CDMA (WCDMA), etc.), fourthgeneration wireless mobile communication technologies (4G) (e.g., longterm evolution (LTE) systems, LTE-Advanced systems, mobile WorldwideInteroperability for Microwave Access (mobile WiMAX) systems, etc.),fifth generation wireless mobile communication technologies (5G) (e.g.,5G New Radio (5G NR) systems, etc.), etc. A mobile communication devicemay utilize a particular RAT to communicate with a network. RATs canoperate in two different domains in a mobile provider network, a circuitswitched (CS) domain or a packet switched (PS) domain. Examples of CSdomain RATs include GSM, WCDMA, etc. Examples of PS domain RATs includeLTE, LTE-Advanced, 5G NR, etc.

Mobile communication devices operating according to the 3rd GenerationPartnership Project (3GPP) technical specifications can be required tosupport emergency calls. Increasing the likelihood that such emergencycalls are successfully established is desirable.

SUMMARY

Systems, methods, and devices of the various aspects may enable a mobilecommunication device to make a second emergency call attempt in a packetswitched (PS) domain in response to determining that a first emergencycall attempt in a PS domain failed. The various aspects may enable asecond emergency call attempt in a PS domain without requiring themobile communication device to attempt an emergency call in a circuitswitched (CS) domain in response to determining that a first emergencycall attempt in a PS domain failed.

Some aspects include a method for performing an emergency call on amobile communication device. Various aspects may include attempting toestablish an emergency call in a PS domain using a first RAT for a firstwireless network, receiving a first indication that the attempt toestablish the emergency call in a PS domain using the first RAT hasfailed, and, in response to the first indication, attempting toestablish the emergency call in a PS domain using a second RAT for asecond wireless network, wherein the second RAT is different from thefirst RAT. In some aspects the mobile communication device may be in anormal service state for the first wireless network with a singlesubscriber identity module or may be in a limited service state for thefirst wireless network. In some aspects, the first wireless network andthe second wireless network may be wireless networks for the samewireless network operator. In some aspects, the first RAT and the secondRAT each may include one of LTE connected to an Evolved Packet Core(EPC), New Radio (NR), or LTE connected to a 5G Core Network (5GCN).

In some aspects, attempting to establish the emergency call in a PSdomain using the second RAT may be based on at least one or more ofconfiguration information in the mobile communication device, anidentity of the first wireless network, an identity of the secondwireless network, a country for the first wireless network, a locationof the mobile communication device, a cause of failure to establish theemergency call in a PS domain using the first RAT, and a secondindication from the first wireless network.

Some aspects may further include receiving a second indication from thefirst wireless network, in which attempting to establish the emergencycall in a PS domain using the second RAT is based at least in part onthe second indication from the first wireless network. In some aspects,the second indication may be received from the first wireless networkusing broadcast or using a Non-Access Stratum (NAS) protocol. In someaspects, the second indication may include an indication that a CircuitSwitched (CS) domain is not available.

In some aspects, attempting to establish the emergency call in a PSdomain using the second RAT may be based at least in part on a cause offailure to establish the emergency call in a PS domain using the firstRAT, and the first indication may include the cause of failure. In someaspects, the cause of failure may indicate a failure for an AccessStratum (AS) or a failure for a NAS.

Some aspects may further include receiving a second indication that theattempt to establish the emergency call in a PS domain using the secondRAT has failed, and attempting to establish the emergency call in a CSdomain using a third RAT for a third wireless network in response to thesecond indication.

Various aspects include a communication device including a processorconfigured with processor-executable instructions to perform operationsof any of the methods summarized above. Various aspects also include anon-transitory processor-readable medium on which is storedprocessor-executable instructions configured to cause a processor of acommunication device to perform operations of any of the methodssummarized above. Various aspects also include a communication deviceincluding means for performing functions of any of the methodssummarized above. Various aspects also include a system on chip for usein a communication device that includes a processor configured toperform one or more operations of any of the methods summarized above.Various aspects also include a system in a package that includes two ormore systems on chip for use in a communication device that includes aprocessor configured to perform one or more operations of any of themethods summarized above.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and constitutepart of this specification, illustrate exemplary aspects of the claims,and together with the general description given above and the detaileddescription given below, serve to explain the features of the claims.

FIG. 1 is a system block diagram conceptually illustrating an examplesystem supporting emergency calls.

FIG. 2 is a component block diagram of a multi-SIM mobile communicationdevice according to various examples.

FIG. 3 is a component block diagram illustrating a communication devicethat may be configured to implement methods for performing an emergencycall in accordance with various embodiments.

FIG. 4A is a signaling flow diagram illustrating a method for performingan emergency call according to various embodiments

FIG. 4B is a process flow diagram illustrating a method for performingan emergency call according to various embodiments.

FIG. 4C is process flow diagram illustrating a method for performing anemergency call according to various embodiments.

FIG. 5 is process flow diagram illustrating a method for performing anemergency call according to various embodiments.

FIG. 6A is process flow diagram illustrating a method for performing anemergency call according to various embodiments.

FIG. 6B is process flow diagram illustrating a method for performing anemergency call according to various embodiments.

FIG. 7 is process flow diagram illustrating a method for performing anemergency call according to various embodiments.

FIG. 8 is process flow diagram illustrating a method for indicatingcircuit switched (CS) domain availability according to variousembodiments.

FIG. 9 is process flow diagram illustrating a method for sending amessage indicating a network emergency retry setting according tovarious embodiments.

FIG. 10 is process flow diagram illustrating a method for setting anetwork emergency retry setting according to various embodiments.

FIG. 11 is a component block diagram of a mobile communication devicethat may be configured to implement methods for performing an emergencycall and/or setting a network emergency retry setting in accordance withvarious embodiments.

FIG. 12 is a component block diagram of a server that may be configuredto implement methods for sending a message indicating a networkemergency retry setting and/or indicating CS domain availability inaccordance with various embodiments.

DETAILED DESCRIPTION

Various aspects will be described in detail with reference to theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.References made to particular examples and implementations are forillustrative purposes, and are not intended to limit the scope of theclaims.

As used herein, the terms “mobile communication device”, “communicationdevice”, and/or “mobile device” refer to any one or all of cellulartelephones, smartphones, portable computing devices, personal or mobilemulti-media players, laptop computers, tablet computers, smartbooks,Internet-of-Things (IoT) devices, palm-top computers, wirelesselectronic mail receivers, multimedia Internet enabled cellulartelephones, wireless gaming controllers, display sub-systems, driverassistance systems, vehicle controllers, vehicle system controllers,vehicle communication system, infotainment systems, vehicle telematicssystems or subsystems, vehicle display systems or subsystems, vehicledata controllers or routers, and similar electronic devices whichinclude a programmable processor and memory and circuitry configured toperform operations as described herein. Mobile communication devices,communication devices, and/or mobile devices may often be referred to asuser equipments (UEs), receiver devices, handsets, etc. While thevarious aspects are particularly useful for emergency communicationsystems, the aspects are generally useful in any communication devicethat includes communication circuitry and a processor that executesapplication programs.

The term “system-on-chip” (SoC) is used herein to refer to a set ofinterconnected electronic circuits typically, but not exclusively,including one or more processors, a memory, and a communicationinterface. The SoC may include a variety of different types ofprocessors and processor cores, such as a general purpose processor, acentral processing unit (CPU), a digital signal processor (DSP), agraphics processing unit (GPU), an accelerated processing unit (APU), asubsystem processor, an auxiliary processor, a single-core processor,and a multicore processor. The SoC may further include other hardwareand hardware combinations, such as a field programmable gate array(FPGA), a configuration and status register (CSR), anapplication-specific integrated circuit (ASIC), other programmable logicdevice, discrete gate logic, transistor logic, registers, performancemonitoring hardware, watchdog hardware, counters, and time references.An SoC may be an integrated circuits (IC) configured such that thecomponents of the IC reside on the same substrate, such as a singlepiece of semiconductor material (e.g., silicon, etc.).

The term system in a package (SIP) is used herein to refer to a singlemodule or package that may contain multiple resources, computationalunits, cores and/or processors on two or more IC chips, substrates, orSoCs. For example, a SIP may include a single substrate on whichmultiple IC chips or semiconductor dies are stacked in a verticalconfiguration. Similarly, the SIP may include one or more multi-chipmodules (MCMs) on which multiple ICs or semiconductor dies are packagedinto a unifying substrate. A SIP may also include multiple independentSoCs coupled together via high speed communication circuitry andpackaged in close proximity, such as on a single motherboard or in asingle mobile communication device. The proximity of the SoCsfacilitates high speed communications and the sharing of memory andresources.

The term “multicore processor” is used herein to refer to a single ICchip or chip package that contains two or more independent processingcores (e.g., CPU core, IP core, GPU core, etc.) configured to read andexecute program instructions. An SoC may include multiple multicoreprocessors, and each processor in an SoC may be referred to as a core.The term “multiprocessor” may be used herein to refer to a system ordevice that includes two or more processing units configured to read andexecute program instructions.

As used herein, the terms subscriber identity module (SIM), “SIM card,”and “subscriber identification module” are used interchangeably to referto a memory that may be an integrated circuit or embedded into aremovable card, and that stores an International Mobile SubscriberIdentity (IMSI), related key, and/or other information used to identifyand/or authenticate a mobile communication device on a network andenable a communication service with the network. Because the informationstored in a SIM enables the mobile communication device to establish acommunication link for a particular communication service with aparticular network, the term “subscription” is used herein as ashorthand reference to refer to the communication service associatedwith and enabled by the information stored in a particular SIM as theSIM and the communication network, as well as the services andsubscriptions supported by that network, correlate to one another. A SIMused in various examples may contain user account information, aninternational mobile subscriber identity (IMSI), a set of SIMapplication toolkit (SAT) commands, and storage space for phone bookcontacts. A SIM card may further store home identifiers (e.g., a SystemIdentification Number (SID)/Network Identification Number (NID) pair, aHome Public Land Mobile Number (HPLMN) code, etc.) to indicate the SIMcard network operator provider. An Integrated Circuit Card Identity(ICCID) SIM serial number may be printed on the SIM card foridentification. However, a SIM may be implemented within a portion ofmemory of the mobile communication device, and thus need not be aseparate or removable circuit, chip or card.

A user may use a subscription on a mobile communication device to makecalls. One type of call is an emergency call, such as calls to police,ambulance, or fire departments. Emergency calls are often establishedbetween a mobile communication device and a public-safety answeringpoint (PSAP). It is important that emergency calls be successfullycompleted quickly.

Emergency sessions and emergency calls from mobile communication devicesmay be supported according to 3rd Generation Partnership Project (3GPP)technical specifications, such as 3GPP; Technical Specification GroupServices and System Aspects; IP Multimedia Subsystem (IMS) EmergencySessions (Release 15) (3GPP TS 23.167 V15.3.0). 3GPP may supportemergency calls in the circuit switched (CS) domain and/or the packetswitched (PS) domain. Different radio access technologies (RATs) mayoperate in the CS domain and the PS domain. CS domain RATs may includeglobal system for mobile communications (GSM), code division multipleaccess (CDMA) 2000 systems, Wideband CDMA (WCDMA), etc. PS domain RATsmay include 5G New Radio (5G NR), long term evolution via a 5G corenetwork (LTE-5GCN), long term evolution via an evolved packet core (EPC)network (LTE-EPC), etc.

The CS domain provides a reliable emergency call service and may be lessprone to errors than PS domain emergency calls. However, the CS domainis gradually being phased out, which will lead to growing areas with noCS coverage. Accordingly, when a mobile communication device attempts toplace an emergency call in the CS domain when no CS coverage is present,the mobile communication device may waste valuable time attempting toconnect an emergency call that will fail as there is no CS coverage.

Many mobile communication devices support attempting emergency callsusing different RATs in different domains. For example, a communicationdevice may support attempting an emergency call in the PS domain using a5G-NR RAT, an LTE-5GCN RAT (in which LTE wireless access may be providedto a 5G core network (5GCN)), and/or an LTE-EPC RAT (in which LTEwireless access may be provided to an enhanced packet core (EPC)network). Additionally, a mobile communication device may supportattempting an emergency call in the CS domain using a WCDMA RAT. When amobile communication device supports establishing an emergency call inat least two different RATs, an emergency call attempted to beestablished in the PS domain using a first RAT may succeed if laterattempted to be established in the PS domain using a different RAT. Forexample, an emergency call whose attempt failed using 5G-NR, may succeedif subsequently attempted using LTE-5GCN or LTE-EPC. Especially when theinitial failure is due to a problem at the access stratum (AS) level ornon-access stratum (NAS) level associated with a first RAT, a secondattempt in the PS domain using a different RAT would likely succeed.Allowing a mobile communication device to make a second emergency callattempt with a different RAT in the PS domain after an unsuccessfulfirst PS domain emergency call attempt may therefore be useful. Whenthere is no CS domain coverage, re-attempting an emergency call in thePS domain with a different RAT may save time in connecting the emergencycall and prevent users from ending the emergency call prematurelybecause the call does not connect within a few seconds time. Forexample, when there is no CS domain coverage, attempting an emergencycall in the CS domain may cause the mobile communication device to waita time period, such as five or more seconds while the CS domain call isattempted. During that wait time, a user may disconnect (or attempt todisconnect) the call due to frustration or an improper understandingthat the emergency call is still being attempted by the network.Avoiding attempting an emergency call in the CS domain when other RATsin the PS domain are available may prevent that wasted time ofattempting a CS domain emergency call when there is no CS domaincoverage.

Systems, methods, and devices of the various aspects may enable a mobilecommunication device to make a second emergency call attempt in a PSdomain in response to determining that a first emergency call attempt inanother PS domain failed. The various aspects may enable a secondemergency call attempt in a PS domain without requiring the mobilecommunication device to attempt an emergency call in a CS domain inresponse to determining that a first emergency call attempt in a PSdomain failed. In various embodiments, a second attempt in a PS domainusing a RAT that is different from the RAT used for a first attempt forthe same emergency call in the PS domain may be performed before any CSdomain attempt for the emergency call is made. In various embodiments,the second attempt in the PS domain using the different RAT may be anattempt to establish the emergency call using a same subscription as wasused for the first attempt in the PS domain. In various embodiments, thedifferent RATs operating in the PS domain for the different emergencycall attempts may be operating in normal mode during each attempt of thesame emergency call.

In various embodiments, a processor of a mobile communication device maybe configured to determine whether one or more different PS domain RATsare available for attempting an emergency call. For example, theprocessor of the mobile communication device may determine the type ofradio frequency (RF) resources available and/or the capabilities of theattached network to determine whether one or more different PS domainRATs are available. The different RATs may include one or more of a5G-NR RAT, a LTE-5GCN RAT, and/or a LTE-EPC RAT. In various embodiments,the processor of the mobile communication device may select one of thedifferent available PS domain RATS as the second RAT. In variousembodiments, the second RAT may be selected based on user preferences,network settings, device conditions, Quality of Service measurements onthe different RATs, or any other criteria that may be used to selectamong the available RATs. The second RAT may be used to attempt toestablish the emergency call in the PS domain in response to determiningthat a first attempt to establish the emergency call in the PS domainwith a first RAT failed. For example, a LTE-5GCN RAT may be selected asthe second RAT when the emergency call initially failed using a 5G-NRRAT. As a further example, a LTE-EPC RAT may be selected as the secondRAT when the emergency call initially failed using a 5G-NR RAT. Asanother example, a LTE-5GCN RAT may be selected as the second RAT whenthe emergency call initially failed using a LTE-EPC RAT. As a furtherexample, a 5G-NR RAT may be selected as the second RAT when theemergency call initially failed using a LTE-EPC RAT. As another example,a LTE-EPC RAT may be selected as the second RAT when the emergency callinitially failed using a LTE-5GCN RAT. As a further example, a 5G-NR RATmay be selected as the second RAT when the emergency call initiallyfailed using a LTE-5GCN RAT.

In various embodiments, a network emergency retry setting may indicatewhether or not the modem should use a PS domain for a second emergencycall attempt. In various embodiments, the network emergency retrysetting may be a setting controlled by a network entity. For example,the network emergency retry setting may indicate whether or not a CSdomain is present in a geographic area. A network entity may determinewhether a CS domain is present and may send a message to a mobilecommunication device indicating whether a CS domain is present. When aCS domain is indicated as not present in the network emergency retrysetting, the mobile communication device may use a PS domain tore-attempt an emergency call in response to a first attempt at theemergency call failing in the PS domain. In some embodiments, thenetwork emergency retry setting may be a setting controlled by themobile communication device.

In various embodiments, a processor of a mobile communication device(e.g., a processor within the modem) may be configured to determinewhether a mobile communication device condition supports using a PSdomain for a second emergency call attempt. As examples, mobilecommunication device conditions may include one or more of a currentlocation of the mobile communication device, a network identity of anetwork to which the mobile communication device is currently attached,a network identify of another network, a country of a network, a settingof the mobile communication device, an operating mode of the mobilecommunication device, etc. As a specific example, in a geographic areaknown to have sporadic or no CS domain coverage, the mobilecommunication device condition may support using a PS domain for asecond emergency call attempt. As another specific example, the mobilecommunication device may recognize a network identity of an attachednetwork as a network in which the PS domain should be used for a secondemergency call attempt.

In various embodiments, the processor of the mobile communication devicemay determine a reason the first attempt to establish an emergency callin a PS domain using a first RAT failed. For example, the processor maydetermine that the initial failure is due to a problem at the AS level,NAS level, or other level of the wireless protocol stacks. In variousembodiments, the reasons for call failure may be associated with using aPS domain for a second emergency call attempt and/or not using a PSdomain for a second emergency call attempt. For example, failures at theAS level and NAS level may be associated with using a PS domain for asecond emergency call attempt, while failures at other levels may not beassociated with using a PS domain for a second emergency call attempt.In response to determining the reason for call failure is associatedwith using a PS domain for a second emergency call attempt, theprocessor may use a PS domain RAT to reattempt the emergency call.

In some embodiments, in response to a subsequent PS domain emergencycall attempt failing, the mobile communication device may attempt toestablish the emergency call in the CS domain. In some embodiments,after a subsequent PS domain emergency call attempt failing, the mobilecommunication device may attempt to establish the emergency call usingother additional PS domain RATs. For example, the mobile communicationdevice may attempt to use three or more different RATs in the PS domainto establish the emergency call.

FIG. 1 illustrates an example system 100 suitable for implementingvarious embodiments. The system 100 may support a mobile communicationdevice 102 performing emergency calls. The system 100 may enableemergency calls from the mobile communication device 102 to beestablished with a public-safety answering point (PSAP) 115 connected toan emergency services Internet Protocol (IP) network (ESInet) 114 usingIP based signaling and/or to an emergency services network (ESN) 118using CS based signaling. For example, the system 100 may supportemergency sessions for the mobile communication device 102 according to3rd Generation Partnership Project (3GPP) technical specifications, suchas 3GPP; Technical Specification Group Services and System Aspects; IPMultimedia Subsystem (IMS) Emergency Sessions (Release 15) (3GPP TS23.167 V15.3.0).

The mobile communication device 102 may establish one or moreconnections with a public land mobile network (PLMN) 111. The mobilecommunication device 102 may include at least one subscriptionsupporting service in the PLMN 111. The PLMN 111 may include a mobileprovider network core 112 connected to different core networks andassociated access networks enabling connections to mobile providernetwork core 112 to be established by the mobile communication device102 using different radio access technologies (RATs). The mobileprovider network core 112 may include one or more types of physicaland/or logical networks to support circuit switched (CS) domain and/orpacket switched (PS) domain services in the PLMN 111, such as an IMScore 116. The PLMN 111 may connect to the ESInet 114, such as viaconnections between the mobile provider network core 112 and the ESInet114 (e.g., via connections between the IMS core 116 and ESInet 114), tosupport establishing emergency calls to the PSAP 115 using IP basedsignaling. The PLMN 111 may connect to the ESN 118, such as viaconnections between the mobile provider network core 112 and the ESN 118(e.g., via connections between the IMS core 116 and ESN 118), to supportestablishing emergency calls to the PSAP 115 using CS based signaling.Some RATs supported in the PLMN 111 may be circuit switched (CS) domainRATs, such as GSM, WCDMA, etc., while other RATs supported in the PLMN111 may be packet switched (PS) domain RATs, such as 5G-NR, LTE-5GCN,LTE-EPC, IEEE 802.11 WiFi (also referred to as Wi-Fi and not shown inFIG. 1), etc. While the PLMN 111 is illustrated as supporting both CSdomain RATs and PS domain RATs, CS domain RATs may not be supported inany given PLMN 111 and/or in specific portions of any given PLMN 111. Insome implementations, one or more PS RATs shown in, or described herein,for FIG. 1 may not be present.

As a specific example, to support the provisioning of a CS domain RAT,one or more Universal Mobile Telecommunications Service (UMTS)Terrestrial Radio Access Networks (UTRAN) 103 may be connected to one ormore Core Networks (CNs) 106 connected to the mobile provider networkcore 112. Via the UTRANs 103, CNs 106, and mobile provider network core112, the PLMN 111 may support CS domain RATs (e.g., WCDMA, etc.) beingused to establish an emergency call in the CS domain by the mobilecommunication device 102 to an ESN 118 connecting the mobile providernetwork core 112 to the PSAP 115.

As another specific example, to support the provisioning of a PS domainRAT, one or more Evolved-UTRANs (E-UTRANs) 104 may be connected to oneor more Evolved Packet Cores (EPC) 107 connected to the mobile providernetwork core 112. Via the E-UTRANs 104, EPCs 107, and mobile providernetwork core 112, the PLMN 111 may support PS domain RATs (e.g.,LTE-EPC, etc.) being used to establish an emergency call by the mobilecommunication device 102 to either an ESInet 114 connecting the mobileprovider network core 112 to the PSAP 115 using IP based signaling or toan ESN 118 connecting the mobile provider network core 112 to the PSAP115 using CS based signaling.

As a further specific example, to support the provisioning of a PSdomain RAT, one or more Next Generation Radio Access Networks (NG-RANs)105 may be connected to one or more 5G Core Networks (5GCNs) 108connected to the mobile provider network core 112. Via the NG-RANs 105and 5GCNs 108, and mobile provider network core 112, the PLMN 111 maysupport PS domain RATs (e.g., LTE-5GCN, 5G NR, etc.) being used toestablish an emergency call by the mobile communication device 102 to anESInet 114 connecting the mobile provider network core 112 to the PSAP115 using IP based signaling or to an ESN 118 connecting the mobileprovider network core 112 to the PSAP 115 using CS based signaling.

E-UTRAN 104 in FIG. 1 may support a Long Term Evolution (LTE) RAT forthe PS domain. NG-RAN 105 in FIG. 1 may support an LTE RAT for the PSdomain using one or more next generation evolved Node Bs (ng-eNBs) inNG-RAN 105 (not shown in FIG. 1). NG-RAN 105 may also or instead supporta Fifth Generation (5G) Next Generation (NR) RAT for the PS domain usingone or more NR Node Bs (also referred as “gNBs”) in NG-RAN 105 (notshown in FIG. 1).

In various aspects, the mobile communication device 102 may beconfigured to establish calls using different RATs. For example, themobile communication device 102 may be configured to establish 5G-NRcalls, LTE-5GCN calls, LTE-EPC calls, GSM calls, and/or WCDMA calls. Invarious aspects, the mobile communication device 102 may be configuredto attempt emergency calls in a CS domain using one or more RATs and/orin a PS domain using one or more RATs.

In various aspects, a mobile provider server 113 connected to the mobileprovider network core 112 may generate and send messages to the mobilecommunication device 102 via the PS domain and/or the CS domain tocontrol which domains (e.g., PS domain, CS domain, PS and CS domains,etc.) the mobile communication device 102 uses for attempting emergencycalls.

In various aspects, the system 100 may include various softwarearchitectures and layered radio protocol stacks at both the mobilecommunication device 102 and in the PLMN 111 to support performingemergency calls. For example, the architectures and stacks may include aNon Access Stratum (NAS) and an Access Stratum (AS). For example, on thenetwork side, the distribution of the NAS and AS protocol layers may besuch that the AS functionality may be provided in the access networks(e.g., UTRAN 103, E-UTRAN 104, NG-RAN 105, etc.) and the NASfunctionality may be provided in the core networks (e.g., CN 106, EPC107, 5GCN 108, etc.). For example, on the mobile communication deviceside, the NAS and AS protocol layers may be implemented in one or moremodem stacks of the mobile communication device 102. In various aspects,the access networks (e.g., UTRAN 103, E-UTRAN 104, NG-RAN 105, etc.)and/or the core networks (e.g., CN 106, EPC 107, 5GCN 108, etc.) maysend indications of reasons that an emergency call failed, such asindications of a failure due to a problem at the AS level, NAS level, orother level, etc., of the wireless protocol stacks, to the mobilecommunication device 102.

FIG. 2 is a functional block diagram of a mobile communication device200 suitable for implementing various aspects. With reference to FIGS.1-2, the mobile communication device 200 may be similar to the mobilecommunication device 102 as described with reference to FIG. 1. Themobile communication device 200 may include one or more SIMs associatedwith one or more different subscriptions.

The mobile communication device 200 may include at least one controller,such as a general processor 206, which may be coupled to a coder/decoder(CODEC) 208. The CODEC 208 may in turn be coupled to a speaker 210 and amicrophone 212. The general processor 206 may also be coupled to thememory 214. The memory 214 may be a non-transitory computer-readablestorage medium that stores processor-executable instructions. Forexample, the instructions may include routing communication data thougha corresponding baseband-RF resource chain. The memory 214 may store anoperating system (OS), as well as user application software andexecutable instructions.

The general processor 206 and the memory 214 may each be coupled to atleast one baseband modem processor 216. Each RAT supported by the mobilecommunication device 200 may be associated with a baseband-RF resourcechain. A baseband-RF resource chain may include the baseband modemprocessor 216, which may perform baseband/modem functions forcommunications with/controlling a RAT supported by the mobilecommunication device 200, and may include one or more amplifiers andradios, referred to generally herein as RF resources (e.g., RF resource218, 219). In some examples, baseband-RF resource chains may share thebaseband modem processor 216 (i.e., a single device that performsbaseband/modem functions for all RATs on the mobile communication device200). In other examples, each baseband-RF resource chain may includephysically or logically separate baseband processors (e.g., BB1, BB2).

The RF resource 218 may be a transceiver that performs transmit/receivefunctions for each of the RATs supported by the mobile communicationdevice 200. The RF resource 218 may include separate transmit andreceive circuitry, or may include a transceiver that combinestransmitter and receiver functions. In some examples, the RF resource218 may include multiple receive circuitries. The RF resource 218 may becoupled to a wireless antenna (e.g., a wireless antenna 220). The RFresource 218 may also be coupled to the baseband modem processor 216. Insome optional examples, the mobile communication device 200 may includeone or more additional optional RF resources 219 configured similarly tothe RF resource 218 and coupled to one or more optional wirelessantennas 221. Each RF resource 218, 219 and antenna 220, 221 may supportone of more different RATs, such as 5G-NR, LTE-5GCN, LTE-EPC, WCDMA,etc. Via the RF resources 218, 219 and the baseband modem processor 216the mobile communication device 200 may establish emergency calls in thePS domain and/or in the CS domain using different RATs.

In some examples, the general processor 206, the memory 214, thebaseband processor(s) 216, and the RF resources 218, 219 may be includedin the mobile communication device 200 as a SIP 250. Further, variousinput and output devices may be coupled to components on thesystem-on-chip 250, such as interfaces or controllers. Example userinput components suitable for use in the mobile communication device 200may include, but are not limited to, a keypad 224, a touchscreen display226, and the microphone 212.

In some examples, the keypad 224, the touchscreen display 226, themicrophone 212, or a combination thereof, may perform the function ofreceiving a request to initiate an outgoing call. For example, thetouchscreen display 226 may receive a selection of a contact from acontact list or receive a telephone number. In another example, eitheror both of the touchscreen display 226 and the microphone 212 mayperform the function of receiving a request to initiate an outgoingcall. For example, the touchscreen display 226 may receive selection ofa contact from a contact list or receive a telephone number. As anotherexample, the request to initiate the outgoing call may be in the form ofa voice command received via the microphone 212. Interfaces may beprovided between the various software modules and functions in themobile communication device 200 to enable communication between them, asis known in the art.

The various embodiments may be implemented on a number of singleprocessor and multiprocessor communication devices, including an SoCand/or an SIP. FIG. 3 illustrates an example SIP 300 architecture thatmay be configured to implement methods for establishing emergency callsin accordance with various embodiments. With reference to FIGS. 1-3,example SIP 300 architecture may be implemented in any SIP, (e.g., SIP250) and may be used in any mobile communication device (e.g., mobilecommunication device 102, mobile communication device 250, etc.)implementing various embodiments.

In the example illustrated in FIG. 3, the SIP 300 includes two SoCs 302,304. In some embodiments, the first SoC 302 may operate as a centralprocessing unit (CPU) of the communication device that carries out theinstructions of software application programs by performing thearithmetic, logical, control and input/output (I/O) operations specifiedby the instructions. In some embodiments, the second SoC 304 may operateas a specialized processing unit. For example, the second SoC 304 mayoperate as a specialized 5G processing unit responsible for managinghigh volume, high speed (e.g., 5 Gbps, etc.), and/or very high frequencyshort wave length (e.g., 28 GHz mmWave spectrum, etc.) communications tosupport 5G NR functionality with an air interface based on orthogonalfrequency-division multiplexing (OFDM). The SoCs and organization offunctionality illustrated in FIG. 3 are a non-limiting example of an SIPas other architectures and organizations of functionality among SoCs,including fewer or more SoCs, are contemplated.

In the example illustrated in FIG. 3, the first SoC 302 includes adigital signal processor (DSP) 310, a modem processor 312, a graphicsprocessor 314, an application processor 316, one or more coprocessors318 (e.g., vector co-processor) connected to one or more of theprocessors, memory 320, custom circuitry 322, system components andresources 324, an interconnection/bus module 326, one or moretemperature sensors 330, and a thermal management unit 332. The secondSoC 304 includes a 5G modem processor 352, a power management unit 354,an interconnection/bus module 364, a plurality of mmWave transceivers356, memory 358, and various additional processors 360, such as anapplications processor, packet processor, etc. Each processor 310, 312,314, 316, 318, 352, 360 may include one or more cores, and eachprocessor/core may perform operations independent of the otherprocessors/cores. For example, the first SoC 302 may include a processorthat executes a first type of operating system (e.g., FreeBSD, LINUX, OSX, etc.) and a processor that executes a second type of operating system(e.g., MICROSOFT WINDOWS 10). In addition, any or all of the processors310, 312, 314, 316, 318, 352, 360 may be included as part of a processorcluster architecture (e.g., a synchronous processor clusterarchitecture, an asynchronous or heterogeneous processor clusterarchitecture, etc.).

The first and second SoCs 302, 304 may include various systemcomponents, resources and custom circuitry for managing sensor data,analog-to-digital conversions, wireless data transmissions, and forperforming other specialized operations, such as decoding data packetsand processing encoded audio and video signals for rendering in a webbrowser or other display application. For example, the system componentsand resources 324 of the first SoC 302 may include power amplifiers,voltage regulators, oscillators, phase-locked loops, peripheral bridges,data controllers, memory controllers, system controllers, access ports,timers, and other similar components used to support the processors andsoftware clients running on a wireless device. The system components andresources 324 and/or custom circuitry 322 may also include circuitry tointerface with peripheral devices, such as cameras, wirelesscommunication devices, external memory chips, display systems, buses,etc.

The first and second SoCs 302, 304 may communicate via one or moreinterconnection/bus modules 350. The processors 310, 312, 314, 316, 318may be interconnected to one or more memory elements 320, systemcomponents and resources 324, and custom circuitry 322, and a thermalmanagement unit 332 via an interconnection/bus module 326. Similarly,the processors 352, 360 may be interconnected to the power managementunit 354, the mmWave transceivers 356, memory 358, and variousadditional processors 360 via the interconnection/bus module 364. Theinterconnection/bus module 326, 350, 364 may include an array ofreconfigurable logic gates and/or implement a bus architecture (e.g.,CoreConnect, AMBA, etc.). Communications may be provided by advancedinterconnects, such as high-performance networks-on chip (NoCs).

The first and/or second SoCs 302, 304 may further include aninput/output module (not illustrated) for communicating with resourcesexternal to the SoCs. Resources external to the SoCs may be shared bytwo or more of the internal SoC processors/cores.

In addition to the SIP 300 discussed above, the various aspects may beimplemented in a wide variety of communication devices, which mayinclude a single processor, multiple processors, multicore processors,or any combination thereof.

FIG. 4A illustrates signaling between a mobile device (user equipment(UE)), a PS Radio Access Network 1 (PS RAN 1), a PS CN 1, an IMS, anESInet, an ESN, a PSAP, a PS RAN 2, a PS CN 2, a CS RAN and a CS CN.With reference to FIGS. 1-4A, the signaling illustrated in FIG. 4A mayenable the performance of an emergency call according to variousembodiments. PS RAN 1 and PS CN 1 may correspond, respectively, toE-UTRAN 104 and EPC 107 in FIG. 1, or to NG-RAN 105 and 5GCN 108 inFIG. 1. PS RAN 2 and PS CN 2 may correspond, respectively, to E-UTRAN104 and EPC 107 in FIG. 1, or to NG-RAN 105 and 5GCN 108 in FIG. 1, andmay both differ from PS RAN 1 and PS CN 1, respectively. CS RAN and CSCN in FIG. 4A may correspond, respectively, to UTRAN 103 and CN 106 inFIG. 1. The ESN and ESInet in FIG. 4A may correspond, respectively, toESN 118 and ESInet 114 in FIG. 1. The UE in FIG. 4A may correspond tothe mobile communication device 102 in FIG. 1. The PSAP in FIG. 4A maycorrespond to PSAP 115 in FIG. 1.

At stage 1 in FIG. 4A, the UE receives an emergency indication. Theemergency indication may correspond to the dialing of an emergencynumber (e.g. “911” or “112”) by a user of the UE, some other indicationof an emergency call or an automatic detection of an emergency condition(e.g., a medical condition for a user of the UE or a fire in abuilding). In response to receiving the emergency indication, the UEdetermines to establish an emergency call and determines to use the PSdomain for a first attempt to establish the emergency call (e.g.,because the UE is already attached to or registered with PS RAN 1 and PSCN 1). The UE also determines a particular RAT for the PS domain and anassociated radio access network (RAN) in which to attempt the emergencycall. In the example in FIG. 4A, the UE determines to use PS RAN 1 andPS CN 1. This may imply attempting the emergency call using an LTE RATconnected to EPC when PS RAN 1 and PS CN 1 correspond to E-UTRAN 104 andEPC 107, respectively. This may instead imply attempting the emergencycall using an LTE RAT connected to 5GCN when PS RAN 1 and PS CN 1correspond to NG-RAN 105 and 5GCN 108, respectively, and when the UEaccesses an ng-eNB in the NG-RAN 105. This may further imply attemptingthe emergency call using an NR RAT when PS RAN 1 and PS CN 1 correspondto NG-RAN 105 and 5GCN 108, respectively, and when the UE accesses a gNBin the NG-RAN 105.

At stage 2 in FIG. 4A, which is optional, the UE may send a request toPS RAN 1 to establish a signaling connection at an Access Stratum (AS)level to PS RAN 1 using the RAT determined at stage 1. Stage 2 may beomitted if the UE already has a signaling connection to PS RAN 1.

At stage 3 in FIG. 4A, the UE may send a request to PS CN 1 (via PSRAN 1) to register with or attach to PS CN 1 at a Non-Access Stratum(NAS) level (e.g., if not yet attached to or registered with PS CN 1).The UE may then send a request to PS CN 1 at the NAS level to eitherestablish an emergency Packet Data Network (PDN) connection (e.g., if PSCN 1 corresponds to EPC 107) or an emergency Packet Data Unit (PDU)session (e.g. if PC CN 1 corresponds to 5GCN 108).

At stage 4 in FIG. 4A, the UE sends a request to the IMS (via PS RAN 1and PS CN 1) to perform an IMS emergency registration.

At stage 5 in FIG. 4A, the UE sends a request (e.g., a SessionInitiation Protocol INVITE message) to the IMS (e.g., via PS RAN 1 andPS CN 1) to request the IMS to attempt to establish an emergency callwith a PSAP. As part of stage 5, the IMS may attempt to establish theemergency call with the PSAP using CS based signaling via ESN 118 orusing IP based signaling via ESInet 114. If the emergency call issuccessfully established with the PSAP, the remaining stages in FIG. 4Aare skipped.

At stage 6, if the first attempt to establish the emergency call fails,the UE may determine a failure at any of stages 2, 3, 4 or 5. For afailure at stage 2, the UE may receive a failure indication and/orfailure cause indicating or implying a failure to establish a signalingconnection at the AS level and may then skip stages 3-5. For a failureat stage 3, the UE may receive a failure indication and/or failure causeindicating or implying a failure to perform a registration or attachmentor to establish an emergency PDN connection or emergency PDU session atthe NAS level and may then skip stages 4-5. For a failure at stage 4,the UE may receive a failure indication and/or failure cause indicatingor implying a failure to perform an IMS emergency registration at theIMS level and may then skip stage 5. For a failure at stage 5, the UEmay receive a failure indication and/or failure cause indicating orimplying a failure to establish an emergency call with a PSAP at theIMS, ESN, ESInet or PSAP level. In some cases, a failure indicationand/or failure cause may be received by the UE after stage 2 andassociated with the AS level or after stage 3 and associated with theNAS level.

At stage 7, the UE determines whether to make a second attempt toestablish the emergency call using the PS domain or CS domain. In someembodiments, if the failure (e.g. failure cause) is associated with theAS level (e.g., occurs at stage 2) or is associated with the NAS level(e.g., occurs at stage 3), the UE may determine to use the PS domain forthe second attempt because use of a different PS RAN and different PS CNmay avoid a recurrence of the same failure. Conversely, if the failureis associated with the IMS level, ESN level, ESInet level or PSAP level(e.g., occurs at stage 4 or stage 5), the UE may determine to use the CSdomain because the CS domain may avoid use of the IMS and/or use of theESInet if stage 5 occurred using the ESInet. Determination to use the PSdomain or CS domain at stage 7 may also be based on an indicationreceived from PS RAN 1 or PS CN 1 (e.g., as part of stage 2 or stage 3and possibly received via broadcast if received from PS RAN 1 orreceived using NAS if received from PS CN 1) indicating that use of theCS domain is or is not required (e.g., use of the CS domain may not berequired and may even be prohibited if there is no CS coverage at thelocation of the UE). The UE may also determine a particular RAT when thePS domain is determined at stage 7; the PS RAT may be different than thePS RAT determined as part of stage 1 (e.g. if NR is determined at stage1, LTE connected to EPC or LTE connected to 5GCN may be determined aspart of stage 7).

If the UE determines to use the PS domain at stage 7 for a secondattempt to establish the emergency call, the UE performs one or more ofstages 8-11 using PS RAN 2 and PS CN 2. Stages 8-11 may be identical orsimilar to stages 2-5 with PS RAN 2 replacing PS RAN 1 and PS CN 2replacing PS CN 1. If the second attempt to establish the emergency callfails (e.g., due to a failure at stage 8, 9, 10, or 11), the UE may makea third attempt to establish the emergency call using the CS domain atstage 13.

If the UE determines to use the CS domain at stage 7 for a secondattempt to establish the emergency call, the UE performs stage 13 toattempt to establish the emergency call using the CS RAN and CS CN.

FIG. 4B illustrates interactions between a mobile device (e.g., mobilecommunication device 102, mobile communication device 200, SIP 300,etc.) and a first wireless network in a PS domain (e.g., a wirelessnetwork including NG-RAN 105 and 5GCN 108, a wireless network includingE-UTRAN 104 and EPC 107, etc.), a second wireless network in a PS domain(e.g., a wireless network including NG-RAN 105 and 5GCN 108, a wirelessnetwork including E-UTRAN 104 and EPC 107, etc.), and a third wirelessnetwork in a CS domain (e.g., a wireless network including UTRAN 103 andCN 106, etc.). With reference to FIGS. 1-4B, the interactionsillustrated in FIG. 4B may enable the performance of an emergency callaccording to various embodiments. In some embodiments, two or more ofthe first wireless network, second wireless network, and third wirelessnetwork may be wireless networks of the same wireless network operator.In various embodiments, the mobile device may include at least a firstRAT and a second RAT. In some embodiments, the first RAT and the secondRAT may be different RATs. As examples, the first RAT and the second RATmay include Long Term Evolution (LTE) connected to an Evolved PacketCore (EPC), New Radio (NR), or LTE connected to a 5G Core Network(5GCN).

In operation 450, the mobile device may receive an indication of anemergency call. For example, the user may initiate an emergency call bydialing a pre-defined emergency number on the mobile device. Asexamples, the emergency indication may correspond to the dialing of anemergency number (e.g., “911” or “112”) by a user of the mobile device,some other indication of an emergency call, or an automatic detection ofan emergency condition (e.g., a medical condition for a user of themobile device).

In operation 452, the mobile device may attempt to establish anemergency call in a PS domain using a first RAT for a first wirelessnetwork. For example, the mobile device may attempt to establish anemergency call in a PS domain using a 5G-NR RAT, an LTE connected to5GCN (LTE-5GCN) RAT, or an LTE connected to EPC (LTE-EPC) RAT. As aspecific example, the first wireless network may be a 5G-NR network(e.g., may include or correspond to NG-RAN 105 and 5GCN 108) and themobile device may attempt to establish an emergency call in a PS domainwith the first wireless network using a 5G-NR RAT (e.g., as describedfor stages 2-5 for FIG. 4A). In some embodiments, the mobile device maybe in a normal service state for the first wireless network, wherein themobile device is subscribed for voice and/or data services with thefirst wireless network. In some embodiments, the mobile device may be ina limited service state for the first wireless network, wherein themobile device is not subscribed for voice and/or data services with thefirst wireless network but is allowed to establish an emergency call.

In operation 454, the attempt to establish the emergency call in a PSdomain using the first RAT for the first wireless network may fail(e.g., as described for stage 6 in FIG. 4A) and the first wirelessnetwork may send one or more indications to the mobile device. In someembodiments, the first wireless network may send a first indication. Forexample, a first indication that may be sent by the first wirelessnetwork may be an indication that the attempt to establish the emergencycall in a PS domain using the first RAT for the first wireless networkhas failed. In some embodiments, the first indication may additionallyindicate a cause of failure of the attempt to establish the emergencycall. As examples, the cause of failure may indicate a failure for anAccess Stratum (AS) or a failure for a Non-Access Stratum (NAS), such asdescribed for stage 6 for FIG. 4A. In some embodiments, the firstwireless network may send one or more additional indications in additionto the first indication. In some embodiments, a second indication fromthe first wireless network may be an indication that a Circuit Switched(CS) domain is not available. In various embodiments, the secondindication may be sent by the first wireless network using broadcastand/or a NAS protocol.

In operation 456, the mobile device may receive the indication that theattempt to establish the emergency call in a PS domain using the firstRAT for the first wireless network has failed. In some embodiments, theindication that the attempt to establish the emergency call in a PSdomain using the first RAT for the first wireless network has failed mayinclude a cause of failure. As examples, the cause of failure mayindicate a failure for an AS (or AS level) or a failure for a NAS (orNAS level). Additionally, the mobile device may receive one or moreother indications, such as a second indication that a CS domain is notavailable or any other type indication. In various embodiments, thesecond indication may be received by the mobile device using broadcastand/or an NAS protocol.

In operation 458, the mobile device may attempt to establish theemergency call in a PS domain using a second RAT for a second wirelessnetwork, such as described for stages 8-11 for FIG. 4A. For example, inresponse to the first indication, the mobile device may attempt toestablish the emergency call in a PS domain using the second RAT for thesecond wireless network. The second RAT may be different than the firstRAT used in operation 452. For example, the mobile device may attempt toestablish an emergency call in a PS domain using a 5G-NR RAT, a LTE-5GCNRAT, or a LTE-EPC RAT that is different than the RAT used in operation452. As a specific example, when the first wireless network is a 5G-NRnetwork and the second wireless network is a LTE-EPC network, the mobiledevice may attempt to establish an emergency call in a PS domain withthe second wireless network using a LTE-EPC RAT in response to theattempt using the 5G-NR RAT failing. In various embodiments, the attemptto establish the emergency call in a PS domain using the second RAT maybe based on at least one of configuration information in the mobiledevice, an identity of the first wireless network, an identity of thesecond wireless network, a country for the first wireless network, alocation of the mobile device, a cause of the failure to establish theemergency call in a PS domain using the first RAT, the second indicationfrom the first wireless network, or some combination of these. As aspecific example, the attempt to establish the emergency call in a PSdomain using the second RAT may be based on the second indication fromthe first wireless network, and the second indication may be receivedfrom the first wireless network using broadcast or using a NAS protocol.As another specific example, the attempt to establish the emergency callin a PS domain using the second RAT may be based on the cause of thefailure to establish the emergency call in a PS domain using the firstRAT and the first indication received by the mobile device may indicatethe cause of failure.

The second attempt to establish the emergency call in a PS domain usingthe second RAT for the second wireless network may succeed or fail. Inresponse to the attempt succeeding, the mobile device and second networkmay establish the emergency call using the second RAT in operation 460.In response to the attempt to establish the emergency call in a PSdomain using the second RAT for the second wireless network failing, thesecond wireless network may send one or more indications to the mobiledevice in operation 462. In some embodiments, the second wirelessnetwork may send a first indication. For example, a first indicationthat may be sent by the second wireless network may be an indicationthat the attempt to establish the emergency call in a PS domain usingthe second RAT for the second wireless network has failed. In someembodiments, the second indication may additionally indicate a cause offailure of the attempt to establish the emergency call. As examples, thecause of failure may indicate a failure for an AS (or AS level) or afailure for a NAS (or NAS level). In some embodiments, the secondwireless network may send one or more additional indications in additionto the first indication. In some embodiments, a second indication fromthe second wireless network may be an indication that a CS domain is notavailable. In various embodiments, the second indication may be sent bythe second wireless network using broadcast and/or a NAS protocol.

In operation 464, the mobile device may receive the indication that theattempt to establish the emergency call in a PS domain using the secondRAT for the second wireless network has failed. In some embodiments, theindication that the attempt to establish the emergency call in a PSdomain using the second RAT for the second wireless network has failedmay include a cause of failure. As examples, the cause of failure mayindicate a failure for an AS or a failure for a NAS. Additionally, themobile device may receive one or more other indications, such as asecond indication that a CS domain is not available or any other typeindication. In various embodiments, the second indication may bereceived by the mobile device using broadcast and/or a NAS protocol.

In operation 466, the mobile device may attempt to establish theemergency call in a CS domain using a third RAT for a third wirelessnetwork, such as described for stage 13 of FIG. 4A. For example, inresponse to the indication from the second wireless network, the mobiledevice may attempt to establish the emergency call in a CS domain usingthe third RAT for the third wireless network. The third RAT may bedifferent than the first RAT used in operation 452 and the second RATused in operation 458. For example, the mobile device may attempt toestablish an emergency call in a CS domain using a GSM RAT or WCDMA RATthat is different than the RAT used in operations 452, 458. As aspecific example, when the first wireless network is a 5G-NR network,the second wireless network is an LTE-EPC network, and the thirdwireless network is a WCDMA network, the mobile device may attempt toestablish an emergency call in a CS domain with the third wirelessnetwork using a WCDMA RAT in response to the attempts using the 5G-NRRAT and LTE-EPC RAT failing.

FIG. 4C illustrates a method 400 for performing an emergency callaccording to various embodiments. With reference to FIGS. 1-4C, theoperations of the method 400 may be performed by a processor of a mobilecommunication devices (e.g., mobile communication device 102, mobilecommunication device 200, SIP 300, etc.).

In block 402, the processor may attempt to establish an emergency callin a PS domain using a first RAT. For example, the mobile communicationdevice may store a database of emergency numbers in memory. If thenumber that the user dials matches one of the emergency numbers, themobile communication device may identify the call as an emergency calland may attempt to establish the emergency call in a PS domain using afirst RAT. For example, the processor may attempt to establish anemergency call in a PS domain using a 5G-NR RAT, a LTE-5GCN RAT, or aLTE-EPC RAT. Emergency calls may be attempted for a variety of otherreasons as well, such as in response to an automatic detection of anemergency condition (e.g., a medical condition for a user of the mobilecommunication device) by a sensor of the mobile communication device,etc.

In determination block 404, the processor may determine whether theattempt to establish the emergency call in a PS domain using the firstRAT failed. For example, the processor may determine whether an errorindication was returned by the network, whether an attempt timerexpired, and/or any other type event occurred during attempting theemergency call to determine whether the attempt to establish theemergency call in a PS domain using the first RAT failed. Alternatively,an indication that the call was successful may indicate the attempt toestablish the emergency call in a PS domain using the first RATsucceeded.

In response to determining that the attempt to establish the emergencycall in a PS domain using the first RAT succeeded (i.e., determinationblock 404=“No”), the processor may conduct the emergency call in a PSdomain using the first RAT in block 408.

In response to determining that the attempt to establish the emergencycall in a PS domain using the first RAT failed (i.e., determinationblock 404=“Yes”), the processor may attempt to establish an emergencycall in a PS domain using a second RAT in block 406. For example, theprocessor may be configured to default to a second RAT different thanthe first RAT based on a user setting, network setting, or otherpredetermined configuration. The second RAT may be a RAT different thanthe first RAT used for the initial attempt of the emergency call. Thesecond RAT may be used to attempt to establish the emergency call in thePS domain in response to determining that a first attempt to establishthe emergency call in the PS domain with a first RAT failed. Forexample, a LTE-5GCN RAT may be selected as the second RAT when theemergency call initially failed using a 5G-NR RAT. As a further example,a LTE-EPC RAT may be selected as the second RAT when the emergency callinitially failed using a 5G-NR RAT. As another example, a LTE-5GCN RATmay be selected as the second RAT when the emergency call initiallyfailed using a LTE-EPC RAT. As a further example, a 5G-NR RAT may beselected as the second RAT when the emergency call initially failedusing a LTE-EPC RAT. As another example, a LTE-EPC RAT may be selectedas the second RAT when the emergency call initially failed using aLTE-5GCN RAT. As a further example, a 5G-NR RAT may be selected as thesecond RAT when the emergency call initially failed using a LTE-5GCNRAT. In various embodiments, the second attempt in the PS domain usingthe second RAT may be an attempt to establish the emergency call usingthe same subscription as was used for the first attempt in the PSdomain. In various embodiments, the different RATs operating in the PSdomain for the different emergency call attempts may be operating innormal mode during each attempt of the same emergency call. For example,both the first RAT and the second RAT may be operating in normal mode.In various embodiments, the first RAT and the second RAT attempting theemergency call may both be using the same subscription and both beoperating in normal mode.

In determination block 410, the processor may determine whether theattempt to establish the emergency call in a PS domain using the secondRAT failed. For example, the processor may determine whether an errorindication was returned by the network, whether an attempt timerexpired, and/or any other type event occurred during attempting theemergency call to determine whether the attempt to establish theemergency call in a PS domain using the second RAT failed.Alternatively, an indication that the call was successful may indicatethe attempt to establish the emergency call in a PS domain using thesecond RAT succeeded.

In response to determining that the attempt to establish the emergencycall in a PS domain using the second RAT succeeded (i.e., determinationblock 410=“No”), the processor may conduct the emergency call in a PSdomain using the second RAT in block 412.

In response to determining that the attempt to establish the emergencycall in a PS domain using the second RAT failed (i.e., determinationblock 410=“Yes”), the processor may attempt to establish an emergencycall in a CS domain in block 414. For example, the processor may attemptto establish the emergency call using a WCDMA RAT. In some embodiments,attempting to establish the call in the CS domain in block 414 may failas no CS domain may be provided by the network at that geographiclocation.

FIG. 5 illustrates a method 500 for performing an emergency callaccording to various embodiments. With reference to FIGS. 1-5, theoperations of the method 500 may be performed by a processor of a mobilecommunication devices (e.g., mobile communication device 102, mobilecommunication device 200, SIP 300, etc.). In some embodiments, theoperations of the method 500 may be performed in conjunction withoperations of the method 400.

In blocks 402, 404, and 408 the processor may perform operations of likenumbered blocks as described with reference to method 400.

In response to determining that the attempt to establish the emergencycall in a PS domain using the first RAT failed (i.e., determinationblock 404=“Yes”), the processor may determine whether one or moredifferent PS domain RATs are available in determination block 502. Forexample, the processor may determine whether the network the mobilecommunication device is currently attached to supports different PSdomain RATs than was used in the first emergency call attempt. Asanother example, the processor may determine whether RF resourcesassociated with different PS domain RATs are available for use on themobile communication device. For example, RF resources for every type PSdomain RAT may not be present on different mobile communication devicesand/or the operating state may be such that an RF resource may beunusable at a given time (e.g., powered down, in a failure state, etc.)

In response to determining that no different PS domain RATs areavailable (i.e., determination block 502=“No”), the processor mayattempt to establish an emergency call in a CS domain in block 414 asdescribed with reference to method 400.

In response to determining that one or more different PS domain RATs areavailable (i.e., determination block 502=“Yes”), the processor mayselect one of the different available PS domain RATs as the second RATin block 504. In various embodiments, the second RAT may be selectedbased on user preferences, network settings, device conditions, Qualityof Service measurements on the different RATs, or any other criteriathat may be used to select among the available RATs.

In blocks 406, 410, 412, and 414 the processor may perform operations oflike numbered blocks as described with reference to method 400.

FIG. 6A illustrates a method 600 for performing an emergency callaccording to various embodiments. With reference to FIGS. 1-6A, theoperations of the method 600 may be performed by a processor of a mobilecommunication devices (e.g., mobile communication device 102, mobilecommunication device 200, SIP 300, etc.). In some embodiments, theoperations of the method 600 may be performed in conjunction withoperations of the methods 400 and/or 500.

In blocks 402, 404, and 408 the processor may perform operations of likenumbered blocks as described with reference to method 400.

In response to determining that the attempt to establish the emergencycall in a PS domain using the first RAT failed (i.e., determinationblock 404=“Yes”), the processor may determine whether a networkemergency retry setting indicates to use a PS domain for a secondemergency call attempt in determination block 602. In variousembodiments, a network emergency retry setting may indicate whether ornot to use a PS domain for a second emergency call attempt. In variousembodiments, the network emergency retry setting may be a settingcontrolled by a network entity. For example, the network emergency retrysetting may indicate whether or not a CS domain is present in ageographic area. A network entity may determine whether a CS domain ispresent and may send a message or an indication to a mobilecommunication device indicating whether a CS domain is present. Forexample, an indication of whether a CS domain is present may be sent bythe network entity (e.g. an AMF) to the mobile communication device inresponse to the sending of a Registration request by the mobile deviceto the network entity when the network entity is an Access and Mobilitymanagement Function (AMF) in 5GCN 108 or in response to the sending ofan Attach request or a Tracking Area Update request by the mobile deviceto the network entity when the network entity is a Mobility ManagementEntity (MME) in EPC 107. When a CS domain is indicated as not present inthe network emergency retry setting, the mobile communication device mayuse a PS domain to re-attempt an emergency call in response to a firstattempt at the emergency call failing in the PS domain. In someembodiments, the network emergency retry setting may be a settingcontrolled by the mobile communication device.

In response to determining that the network emergency retry setting doesnot indicate to use a PS domain for a second emergency call attempt(i.e., determination block 602=“No”), the processor may attempt toestablish an emergency call in a CS domain in block 414 as describedwith reference to method 400.

In response to determining that the network emergency retry setting doesindicate to use a PS domain for a second emergency call attempt (i.e.,determination block 602=“Yes”), in blocks 502, 504, 406, 410, 412, and414 the processor may perform operations of like numbered blocks asdescribed with reference to methods 400 and 500.

FIG. 6B illustrates a method 650 for performing an emergency callaccording to various embodiments. With reference to FIGS. 1-6B, theoperations of the method 650 may be performed by a processor of a mobilecommunication devices (e.g., mobile communication device 102, mobilecommunication device 200, SIP 300, etc.). In some embodiments, theoperations of the method 650 may be performed in conjunction withoperations of the methods 400, 500, and/or 600.

In blocks 402, 404, and 408 the processor may perform operations of likenumbered blocks as described with reference to method 400.

In response to determining that the attempt to establish the emergencycall in a PS domain using the first RAT failed (i.e., determinationblock 404=“Yes”), the processor may determine whether a device conditionsupports using a PS domain for a second emergency call attempt indetermination block 652. As examples, mobile communication deviceconditions may include one or more of a current location of the mobilecommunication device, a network identity of a network to which themobile communication device is currently attached, a network identify ofanother network, a country of a network, a setting of the mobilecommunication device, an operating mode of the mobile communicationdevice, etc. As a specific example, in a geographic area known to havesporadic or no CS domain coverage, the mobile communication devicecondition may support using a PS domain for a second emergency callattempt if a current location of the mobile device or a network identityof a network to which the mobile communication device is currentlyattached indicates that the mobile device is, or may be, in thegeographic area. As another specific example, the mobile communicationdevice may recognize a network identity of an attached network as anetwork in which the PS domain should be used for a second emergencycall attempt.

In response to determining that a device condition does not supportusing a PS domain for a second emergency call attempt (i.e.,determination block 652=“No”), the processor may attempt to establish anemergency call in a CS domain in block 414 as described with referenceto method 400.

In response to determining that a device condition does support using aPS domain for a second emergency call attempt (i.e., determination block652=“Yes”), in blocks 502, 504, 406, 410, 412, and 414 the processor mayperform operations of like numbered blocks as described with referenceto methods 400 and 500.

FIG. 7 illustrates a method 700 for performing an emergency callaccording to various embodiments. With reference to FIGS. 1-7, theoperations of the method 700 may be performed by a processor of a mobilecommunication devices (e.g., mobile communication device 102, mobilecommunication device 200, SIP 300, etc.). In some embodiments, theoperations of the method 700 may be performed in conjunction withoperations of the methods 400, 500, 600, and/or 650.

In blocks 402, 404, 408, and 502 the processor may perform operations oflike numbered blocks as described with reference to methods 400 and 500.

In response to determining that one or more different PS domain RATs areavailable (i.e., determination block 502=“Yes”), the processor maydetermine a reason for why the first attempt to establish the emergencycall in a PS domain using the first RAT failed in block 702. In variousembodiments, the processor of the mobile communication device maydetermine a reason the first attempt to establish an emergency call in aPS domain using a first RAT failed. For example, the processor maydetermine the initial failure is due to a problem at the AS level, NASlevel, or other level of the wireless protocol stacks.

In determination block 704, the processor may determine whether thereason is associated with using a PS domain for a second emergency callattempt. In various embodiments, the reasons for call failure may beassociated with using a PS domain for a second emergency call attemptand/or not using a PS domain for a second emergency call attempt. Forexample, failures at the AS level and NAS level may be associated withusing a PS domain for a second emergency call attempt, while failures atother levels may not be associated with using a PS domain for a secondemergency call attempt. In response to determining the reason for callfailure is associated with using a PS domain for a second emergency callattempt, the processor may use a PS domain RAT to reattempt theemergency call.

In response to determining that the reason is not associated with usinga PS domain for a second emergency call attempt (i.e., determinationblock 704=“No”), the processor may attempt to establish an emergencycall in a CS domain in block 414 as described with reference to method400.

In response to determining that the reason is associated with using a PSdomain for a second emergency call attempt (i.e., determination block704=“Yes”), in blocks 504, 406, 410, 412, and 414 the processor mayperform operations of like numbered blocks as described with referenceto methods 400 and 500.

FIG. 8 illustrates a method 800 for indicating CS domain availabilityaccording to various embodiments. With reference to FIGS. 1-8, theoperations of the method 800 may be performed by a processor of a server(e.g., mobile provider server 113, etc.). In some embodiments, theoperations of the method 800 may be performed in conjunction withoperations of the methods 400, 500, 600, 650, and/or 700.

In determination block 802, the server may determine whether a CS domainis available. A network entity may determine whether a CS domain ispresent and may send a message to a mobile communication deviceindicating whether a CS domain is present. For example, a network entitymay determine whether a CS domain is present in different geographicregions of a network.

In response to determining that the CS domain is available (i.e.,determination block 802=“Yes”), the server may send a message indicatingthe CS domain is available in block 804. For example, the message may bea message indicating a network emergency retry setting indicating the CSdomain is available. The message may be sent to a mobile communicationdevice via one or more RATs.

In response to determining that the CS domain is not available (i.e.,determination block 802=“No”), the server may send a message indicatingthe CS domain is not available in block 806. For example, the messagemay be a message indicating a network emergency retry setting indicatingthe CS domain is not available. The message may be sent to a mobilecommunication device via one or more RATs.

FIG. 9 illustrates a method 900 for sending a message indicating anetwork emergency retry setting according to various embodiments. Withreference to FIGS. 1-9, the operations of the method 900 may beperformed by a processor of a server (e.g., mobile provider server 113,etc.). In some embodiments, the operations of the method 900 may beperformed in conjunction with operations of the methods 400, 500, 600,650, 700, and/or 800.

In block 902, the server may select a network emergency retry setting.In various embodiments, the network emergency retry setting may be asetting controlled by a network entity. For example, the networkemergency retry setting may indicate whether or not a CS domain ispresent in a geographic area. Additionally, the network emergency retrysetting may indicating whether a mobile communication device is to use aPS domain to reattempt an emergency call in response to a first attemptat the emergency call failing in the PS domain or the mobilecommunication device is to use a CS domain to reattempt an emergencycall in response to a first attempt at the emergency call failing in thePS domain.

In block 904, the server may generate and send a message indicating thenetwork emergency retry setting. The message may be sent to a mobilecommunication device via one or more RATs.

FIG. 10 illustrates a method 1000 for setting a network emergency retrysetting according to various embodiments. With reference to FIGS. 1-10,the operations of the method 1000 may be performed by a processor of amobile communication devices (e.g., mobile communication device 102,mobile communication device 200, SIP 300, etc.). In some embodiments,the operations of the method 1000 may be performed in conjunction withoperations of the methods 400, 500, 600, 650, 700, 800, and/or 900.

In optional block 1002, the processor may receive a message. Block 1002may be optional as not all networks may send messages related to networkemergency retry settings to mobile communication devices. The messagemay include an indication of a network emergency retry setting. Thenetwork emergency retry setting may be a setting controlled by a networkentity. For example, the network emergency retry setting may indicatewhether or not a CS domain is present in a geographic area.Additionally, the network emergency retry setting may indicating whethera mobile communication device is to use a PS domain to reattempt anemergency call in response to a first attempt at the emergency callfailing in the PS domain or the mobile communication device is to use aCS domain to reattempt an emergency call in response to a first attemptat the emergency call failing in the PS domain.

In optional block 1004, the processor may determine CS domainavailability. Block 1004 may be optional as not all mobile communicationdevices may be configured to determine CS domain availability.Alternatively, some may have CS domain availability indicated bymessages from the network. When a processor is configured to determineCS domain availability, the processor may perform operations to detectand/or test the operation of a CS domain RAT. For example, the processormay attempt to attach to a CS domain of a network to determine CS domainavailability. Additionally, the processor may determine CS domainavailability in other manners, such as by monitoring settings and/ornetwork level indications.

In block 1006, the processor may set the network emergency retrysetting. The network emergency retry setting may indicate whether or nota CS domain is present in a geographic area. Additionally, the networkemergency retry setting may indicating whether a mobile communicationdevice is to use a PS domain to reattempt an emergency call in responseto a first attempt at the emergency call failing in the PS domain or themobile communication device is to use a CS domain to reattempt anemergency call in response to a first attempt at the emergency callfailing in the PS domain. The network emergency retry setting may be setby the mobile communication device based on one or more of the receivedmessages, determinations of the CS domain availability, and/or otherfactors.

The various aspects (including, but not limited to, embodimentsdiscussed above with reference to FIGS. 1-10) may be implemented on avariety of mobile communication devices, an example of which isillustrated in FIG. 11 in the form of a smartphone. With reference toFIGS. 1-11, a smartphone 1100 may include a first SoC 1102 (e.g., aSoC-CPU) coupled to a second SoC 1124 (e.g., a 5G capable SoC) and athird SoC 1116 (e.g., a SoC configured for managing device-to-device(D2D) links, such as D2D links establish in the dedicated IntelligentTransport System (ITS) 5.9 GHz spectrum communications). The first,second, and/or third SoCs 1102, 1124, and 1116 may be coupled tointernal memory 1106, a display 1112, and to a speaker 1114.Additionally, the smartphone 1100 may include one or more antenna 1104for sending and receiving electromagnetic radiation that may beconnected to one or more transceiver 1108 (e.g., a wireless data linkand/or cellular transceiver, etc.) coupled to one or more processors inthe first, second, and/or third SoCs 1102, 1124, and 1116. Smartphones1100 typically also include menu selection buttons or rocker switches1120 for receiving user inputs.

A typical smartphone 1100 also includes a sound encoding/decoding(CODEC) circuit 1110, which digitizes sound received from a microphoneinto data packets suitable for wireless transmission and decodesreceived sound data packets to generate analog signals that are providedto the speaker to generate sound. Also, one or more of the processors inthe first, second, and/or third SoCs 1102, 1124, and 1116, transceiver1108 and CODEC circuit 1110 may include a digital signal processor (DSP)circuit (not shown separately).

The various embodiments (including, but not limited to, embodimentsdiscussed above with reference to FIGS. 1-10) may also be implemented onany of a variety of commercially available server devices, such as theserver 1200 illustrated in FIG. 12. Such a server 1200 typicallyincludes a processor 1201 coupled to volatile memory 1202 and a largecapacity nonvolatile memory, such as a disk drive 1203. The server 1200may also include a floppy disc drive, compact disc (CD) or digitalversatile disc (DVD) disc drive 1206 coupled to the processor 1201. Theserver 1200 may also include one or more wired or wireless networktransceivers 1204, such one or more network access ports and/or wired orwireless modems (e.g., one wired or wireless modem, two wired orwireless modems, three wired or wireless modems, four wired or wirelessmodems, or more than four wired or wireless modems), coupled to theprocessor 1201 for establishing network interface connections with oneor more communication networks 1207, such as a local area network (e.g.,Ethernet, etc.) coupled to other computing devices and/or servers, theInternet, the public switched telephone network, and/or one or morecellular networks (e.g., CDMA, GSM, LTE, 5G, or any other type ofcellular network).

The processors implementing various embodiments may be any programmablemicroprocessor, microcomputer or multiple processor chip or chips thatcan be configured by software instructions (applications) to perform avariety of functions, including the functions of the various aspectsdescribed in this application. In some communication devices, multipleprocessors may be provided, such as one processor dedicated to wirelesscommunication functions and one processor dedicated to running otherapplications. Typically, software applications may be stored in theinternal memory before they are accessed and loaded into the processor.The processor may include internal memory sufficient to store theapplication software instructions.

As used in this application, the terms “component,” “module,” “system,”and the like are intended to include a computer-related entity, such as,but not limited to, hardware, firmware, a combination of hardware andsoftware, software, or software in execution, which are configured toperform particular operations or functions. For example, a component maybe, but is not limited to, a process running on a processor, aprocessor, an object, an executable, a thread of execution, a program,and/or a computer. By way of illustration, both an application runningon a processor of a communication device and the communication devicemay be referred to as a component. One or more components may residewithin a process and/or thread of execution and a component may belocalized on one processor or core and/or distributed between two ormore processors or cores. In addition, these components may execute fromvarious non-transitory computer readable media having variousinstructions and/or data structures stored thereon. Components maycommunicate by way of local and/or remote processes, function orprocedure calls, electronic signals, data packets, memory read/writes,and other known network, computer, processor, and/or process relatedcommunication methodologies.

A number of different cellular and mobile communication services andstandards are available or contemplated in the future, all of which mayimplement and benefit from the various aspects. Such services andstandards may include, e.g., third generation partnership project(3GPP), long term evolution (LTE) systems, third generation wirelessmobile communication technology (3G), fourth generation wireless mobilecommunication technology (4G), fifth generation wireless mobilecommunication technology (5G), global system for mobile communications(GSM), universal mobile telecommunications system (UMTS), 3GSM, generalpacket radio service (GPRS), code division multiple access (CDMA)systems (e.g., cdmaOne, CDMA1020™), EDGE, advanced mobile phone system(AMPS), digital AMPS (IS-136/TDMA), evolution-data optimized (EV-DO),digital enhanced cordless telecommunications (DECT), WorldwideInteroperability for Microwave Access (WiMAX), wireless local areanetwork (WLAN), Wi-Fi Protected Access I & II (WPA, WPA2), integrateddigital enhanced network (iden), Cellular Vehicle-to-Everything (C-V2X),etc. Each of these technologies involves, for example, the transmissionand reception of voice, data, signaling, and/or content messages. Itshould be understood that any references to terminology and/or technicaldetails related to an individual telecommunication standard ortechnology are for illustrative purposes only, and are not intended tolimit the scope of the claims to a particular communication system ortechnology unless specifically recited in the claim language.

Various aspects illustrated and described are provided merely asexamples to illustrate various features of the claims. However, featuresshown and described with respect to any given aspect are not necessarilylimited to the associated aspect and may be used or combined with otheraspects that are shown and described. Further, the claims are notintended to be limited by any one example aspect. For example, one ormore of the operations of the methods may be substituted for or combinedwith one or more operations of the methods.

The foregoing method descriptions and the process flow diagrams areprovided merely as illustrative examples and are not intended to requireor imply that the operations of various aspects must be performed in theorder presented. As will be appreciated by one of skill in the art theorder of operations in the foregoing aspects may be performed in anyorder. Words such as “thereafter,” “then,” “next,” etc. are not intendedto limit the order of the operations; these words are used to guide thereader through the description of the methods. Further, any reference toclaim elements in the singular, for example, using the articles “a,”“an,” or “the” is not to be construed as limiting the element to thesingular.

Various illustrative logical blocks, modules, components, circuits, andalgorithm operations described in connection with the aspects disclosedherein may be implemented as electronic hardware, computer software, orcombinations of both. To clearly illustrate this interchangeability ofhardware and software, various illustrative components, blocks, modules,circuits, and operations have been described above generally in terms oftheir functionality. Whether such functionality is implemented ashardware or software depends upon the particular application and designconstraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such aspect decisions should not beinterpreted as causing a departure from the scope of the claims.

The hardware used to implement various illustrative logics, logicalblocks, modules, and circuits described in connection with the aspectsdisclosed herein may be implemented or performed with a general purposeprocessor, a digital signal processor (DSP), an ASIC, a fieldprogrammable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but, in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of receiver smart objects, e.g., acombination of a DSP and a microprocessor, a plurality ofmicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration. Alternatively, some operations ormethods may be performed by circuitry that is specific to a givenfunction.

In one or more aspects, the functions described may be implemented inhardware, software, firmware, or any combination thereof. If implementedin software, the functions may be stored as one or more instructions orcode on a non-transitory computer-readable storage medium ornon-transitory processor-readable storage medium. The operations of amethod or algorithm disclosed herein may be embodied in aprocessor-executable software module or processor-executableinstructions, which may reside on a non-transitory computer-readable orprocessor-readable storage medium. Non-transitory computer-readable orprocessor-readable storage media may be any storage media that may beaccessed by a computer or a processor. By way of example but notlimitation, such non-transitory computer-readable or processor-readablestorage media may include RAM, ROM, EEPROM, FLASH memory, CD-ROM orother optical disk storage, magnetic disk storage or other magneticstorage smart objects, or any other medium that may be used to storedesired program code in the form of instructions or data structures andthat may be accessed by a computer. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk, and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofnon-transitory computer-readable and processor-readable media.Additionally, the operations of a method or algorithm may reside as oneor any combination or set of codes and/or instructions on anon-transitory processor-readable storage medium and/orcomputer-readable storage medium, which may be incorporated into acomputer program product.

The preceding description of the disclosed aspects is provided to enableany person skilled in the art to make or use the claims. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects without departing from the scope of the claims. Thus, thepresent disclosure is not intended to be limited to the aspects shownherein but is to be accorded the widest scope consistent with thefollowing claims and the principles and novel features disclosed herein.

What is claimed is:
 1. A method for performing an emergency call on a mobile communication device, comprising: attempting, by a processor of the mobile communication device, to establish an emergency call in a Packet Switched (PS) domain using a first radio access technology (RAT) for a first wireless network; receiving, by the processor, a first indication that the attempt to establish the emergency call in a PS domain using the first RAT has failed; determining, by the processor, whether the first indication indicates a failure above a Non-Access Stratum (NAS) level; attempting, by the processor, to establish the emergency call in a PS domain using a second RAT for a second wireless network in response to determining that the first indication does not indicate the failure above the NAS level, and wherein the second RAT is different from the first RAT; and attempting, by the processor, to establish the emergency call in a Circuit Switched (CS) domain using a third RAT for a third wireless network in response to determining that the first indication does indicate the failure above the NAS level.
 2. The method of claim 1, wherein the mobile communication device is in a normal service state for the first wireless network with a single subscriber identity module or is in a limited service state for the first wireless network.
 3. The method of claim 1, wherein attempting to establish the emergency call in a PS domain using the second RAT is based on at least one or more of configuration information in the mobile communication device, an identity of the first wireless network, an identity of the second wireless network, a country for the first wireless network, a location of the mobile communication device, a cause of failure to establish the emergency call in a PS domain using the first RAT, and a second indication from the first wireless network.
 4. The method of claim 1, further comprising receiving, by the processor, a second indication from the first wireless network, wherein attempting to establish the emergency call in a PS domain using the second RAT is based at least in part on the second indication from the first wireless network.
 5. The method of claim 4, wherein the second indication is received from the first wireless network using broadcast or using a Non-Access Stratum (NAS) protocol.
 6. The method of claim 4, wherein the second indication comprises an indication that a Circuit Switched (CS) domain is not available.
 7. The method of claim 1, further comprising: receiving, by the processor, a second indication that the attempt to establish the emergency call in a PS domain using the second RAT has failed; and attempting, by the processor, to establish the emergency call in a CS domain using the third RAT for the third wireless network in response to the second indication.
 8. The method of claim 1, wherein the first wireless network and the second wireless network comprise wireless networks for the same wireless network operator.
 9. The method of claim 1, wherein the first RAT and the second RAT each comprise one of Long Term Evolution (LTE) connected to an Evolved Packet Core (EPC), New Radio (NR), or LTE connected to a 5G Core Network (5GCN).
 10. A mobile communication device, comprising: a processor configured with processor-executable instructions to perform operations comprising: attempting to establish an emergency call in a Packet Switched (PS) domain using a first radio access technology (RAT) for a first wireless network; receiving a first indication that the attempt to establish the emergency call in a PS domain using the first RAT has failed; determining whether the first indication indicates a failure above a Non-Access Stratum (NAS) level; attempting to establish the emergency call in a PS domain using a second RAT for a second wireless network in response to determining that the first indication does not indicate the failure above the NAS level, and wherein the second RAT is different from the first RAT; and attempting to establish the emergency call in a Circuit Switched (CS) domain using a third RAT for a third wireless network in response to determining that the first indication does indicate the failure above the NAS level.
 11. The mobile communication device of claim 10, wherein the processor is configured with processor-executable instructions to perform operations such that attempting to establish the emergency call in a PS domain using the second RAT is based on at least one or more of configuration information in the mobile communication device, an identity of the first wireless network, an identity of the second wireless network, a country for the first wireless network, a location of the mobile communication device, a cause of failure to establish the emergency call in a PS domain using the first RAT, and a second indication from the first wireless network.
 12. The mobile communication device of claim 10, wherein the processor is configured with processor-executable instructions to perform operations further comprising receiving a second indication from the first wireless network, wherein attempting to establish the emergency call in a PS domain using the second RAT is based at least in part on the second indication from the first wireless network.
 13. The mobile communication device of claim 12, wherein the processor is configured with processor-executable instructions to perform operations such that the second indication is received from the first wireless network using broadcast or using a Non-Access Stratum (NAS) protocol.
 14. The mobile communication device of claim 12, wherein the processor is configured with processor-executable instructions to perform operations such that the second indication comprises an indication that a Circuit Switched (CS) domain is not available.
 15. The mobile communication device of claim 10, wherein the processor is configured with processor-executable instructions to perform operations further comprising: receiving a second indication that the attempt to establish the emergency call in a PS domain using the second RAT has failed; and in response to the second indication, attempting to establish the emergency call in a CS domain using the third RAT for the third wireless network.
 16. A non-transitory processor-readable storage medium having stored thereon processor-executable instructions configured to cause a processor of a mobile communication device to perform operations comprising: attempting to establish an emergency call in a Packet Switched (PS) domain using a first radio access technology (RAT) for a first wireless network; receiving a first indication that the attempt to establish the emergency call in a PS domain using the first RAT has failed; determining whether the first indication indicates a failure above a Non-Access Stratum (NAS) level; attempting to establish the emergency call in a PS domain using a second RAT for a second wireless network in response to determining that the first indication does not indicate the failure above the NAS level, and wherein the second RAT is different from the first RAT; and attempting to establish the emergency call in a Circuit Switched (CS) domain using a third RAT for a third wireless network in response to determining that the first indication does indicate the failure above the NAS level. 